beta-2 agonist

Examples of beta-2 agonist in the following topics:

• Adrenergic Neurons and Receptors

  • Many cells possess these receptors, and the binding of an agonist will generally cause a sympathetic (or sympathomimetic) response (e.g., the fight-or-flight response).
  • Phenylephrine is a selective agonist of the α receptor.
  • Agonist binding thus causes a rise in the intracellular concentration of the second messenger cAMP.
  • Isoprenaline is a nonselective agonist.

• Asthma

  • Treatment of acute symptoms is usually with an inhaled short-acting beta-2 agonist (such as salbutamol).
  • The most common triggers include allergens, smoke (tobacco and other), air pollution, non selective beta-blockers, and sulfite-containing foods.

• Agonists, Antagonists, and Drugs

  • Agonists increase the level of receptor activation, antagonists reduce it.
  • Most indirect-acting ACh receptor agonists work by inhibiting the enzyme acetylcholinesterase.
  • Beta blockers (sometimes written as β-blockers) or beta-adrenergic blocking agents, beta-adrenergic antagonists, beta-adrenoreceptor antagonists, or beta antagonists, are a class of drugs used for various indications.
  • As beta-adrenergic receptor antagonists, they diminish the effects of epinephrine (adrenaline) and other stress hormones.
  • Distinguish between the effects of an agonist versus an antagonist in the autonomic nervous system

• Direct Gene Activation and the Second-Messenger System

  • The G-protein is bound to the inner membrane of the cell and consists of three sub-units: alpha, beta, and gamma.
  • Upon binding to the receptor, it releases a GTP molecule, at which point the alpha sub-unit of the G-protein breaks free from the beta and gamma sub-units and is able to move along the inner membrane until it contacts another membrane-bound protein: the primary effector. 
  • The agonist activates the membrane-bound receptor. 2.

• Cholinergic Neurons and Receptors

  • In the cerebral cortex, tonic ACh inhibits layer 4 neurons, the main targets of thalamocortical inputs while exciting pyramidal cells in layers 2/3 and 5.
  • This filters out weak sensory inputs in layer 4 and amplifies inputs that reach the layers 2/3 and layer 5 excitatory microcircuits.
  • The result was also found in Alzheimer's disease patients and smokers after nicotine (an ACh agonist) consumption.
  • The heteromeric receptors found in the central nervous system are made up of 2 α and 3 β subunits with the binding site at the interface of α and adjacent subunit.

• Blood Plasma

  • Human blood plasma volume averages about 2.7–3.0 liters.
  • Globulins are a diverse group of proteins designated into three groups, gamma, alpha, and beta, based on how far they move during electrophoresis tests.
  • For example, the beta globulin transferrin can transport iron.
  • Alpha globulins are notable for inhibiting certain proteases, while beta globulins often function as enzymes in the body.

• Insulin Secretion and Regulation of Glucagon

  • Insulin is produced by beta cells in the pancreas and acts to oppose the functions of glucagon.
  • Patients with type 2 diabetes are often insulin resistant and, because of such resistance, they may suffer from a relative insulin deficiency.
  • Some patients with type 2 diabetes may eventually require insulin if other medications fail to control blood glucose levels adequately.

• Basement Membranes and Diseases

  • The electron-dense lamina densa membrane is about 30–70 nanometers in thickness, and consists of an underlying network of reticular collagen (type IV) fibrils (fibroblast precursors) which average 30 nanometers in diameter and 0.1–2 micrometers in thickness.
  • It is caused by a mutation in the integrin α6β4 cell-adhesion molecule on either the alpha or beta subunit.

• Platelets

  • Platelets are irregularly shaped, have no nucleus, and typically measure only 2–3 micrometers in diameter.
  • They also release wound healing-associated growth factors including platelet-derived growth factor (PDGF), which directs cell movement; TGF beta, which stimulates the deposition of extracellular matrix tissue into a wound during healing; and vascular endothelial growth factor (VEGF), which stimulates angiogenesis, or the regrowth of blood vessels.

• Congestive Heart Failure

  • In developed countries, around 2% of adults suffer from heart failure, but in those over the age of 65, this increases to 6–10%.
  • In developing countries, 2-3% percent of the population suffers from heart failure, but in those 70 to 80 years old, it occurs in 20-30%.
  • Binding to beta-1 receptors in the myocardium increases the heart rate and make contractions more forceful, in an attempt to increase cardiac output.